docs: def zscore(self, axis=1):
          """
          Subtract the mean and divide by standard deviation within or across records.
  
          Parameters
          ----------
          axis : int, optional, default = 0
              Which axis to zscore along, within (1) or across (0) records
          """
          if axis == 1:
              return self.map(lambda x: (x - mean(x)) / std(x))
          elif axis == 0:
              meanval = self.mean().toarray()
              stdval = self.std().toarray()
              return self.map(lambda x: (x - meanval) / stdval)
          else:
              raise Exception('Axis must be 0 or 1')